What is the recommended antibiotic therapy for a patient with acute appendicitis?

Antibiotic Therapy for Acute Appendicitis

Surgical Management (Standard Approach)

For uncomplicated appendicitis undergoing surgery, give a single preoperative dose of broad-spectrum antibiotics (such as piperacillin-tazobactam 3.375g IV) within 0-60 minutes before incision, and stop all antibiotics immediately postoperatively—no postoperative antibiotics are needed. 1, 2

Uncomplicated Appendicitis (No Perforation/Abscess)

• Preoperative: Administer one dose of broad-spectrum antibiotics covering enteric gram-negatives and anaerobes 0-60 minutes before surgical incision 1, 2

• Recommended agents:

  • Piperacillin-tazobactam 3.375g IV (preferred) 1, 3
  • Cefoxitin 2g IV 1
  • Alternative: Ampicillin-sulbactam, ticarcillin-clavulanate, or carbapenems 2

• Postoperative: Discontinue antibiotics immediately after surgery—no postoperative course is indicated 1, 2

• Evidence strength: Multiple high-quality guidelines consistently demonstrate that a single preoperative dose effectively reduces wound infections and intra-abdominal abscesses, while postoperative antibiotics provide no additional benefit 1, 2

Complicated Appendicitis (Perforation/Abscess/Gangrenous)

For complicated appendicitis with adequate source control achieved at surgery, limit postoperative antibiotics to 3-5 days maximum, or discontinue after 24 hours if complete source control was achieved. 1, 2

• Preoperative: Same single dose as uncomplicated cases 1

• Postoperative duration:

  • If complete source control achieved (complete appendectomy, no residual abscess/purulence): Stop antibiotics after 24 hours 1, 2
  • If adequate but not complete source control: Continue for 3-5 days maximum 1, 2
  • Prolonged courses beyond 5 days provide no additional benefit 1, 2

• Recommended postoperative regimens for complicated cases:

  • Imipenem-cilastatin 1g IV every 8 hours 1
  • Meropenem 1g IV every 8 hours 1
  • Piperacillin-tazobactam 3.375g IV every 6 hours 2, 3

• Critical pitfall: Do not confuse gangrenous with perforated appendicitis—gangrenous appendicitis without perforation should be treated like uncomplicated appendicitis with antibiotics stopped after 24 hours 2

Antibiotics to Avoid

• Do NOT use ampicillin-sulbactam due to E. coli resistance rates exceeding 20% 1
• Avoid cefotetan or clindamycin due to increasing Bacteroides fragilis resistance 1

Non-Operative Management (Antibiotics Alone)

For patients treated non-operatively with antibiotics alone, administer minimum 48 hours IV antibiotics followed by oral antibiotics for a total duration of 7-10 days. 1

• IV regimen: Piperacillin-tazobactam 3.375g IV every 6 hours for minimum 48 hours 1, 4

• Oral transition: Ciprofloxacin plus metronidazole to complete 7-10 days total 1, 4

• Success rate: Approximately 63-77% of patients remain asymptomatic at 1 year without surgery 5, 6, 4

• Predictors of failure: Appendicolith on CT, appendiceal diameter >13mm, or mass effect predict 40% failure rate—these patients should undergo surgery if fit 5

• Mandatory follow-up: Patients ≥40 years treated non-operatively require colonoscopy and interval contrast-enhanced CT due to 3-17% incidence of appendiceal neoplasms 1, 2

Pediatric Patients

Non-Perforated Appendicitis in Children

• Preoperative: Single dose of cefoxitin or cefotetan (weight-based dosing) 1
• Postoperative: No antibiotics recommended 1, 2

Complicated Appendicitis in Children

• Regimens: Piperacillin-tazobactam, ampicillin-sulbactam, or ticarcillin-clavulanate (weight-based dosing) 1, 2
• Duration: Switch to oral antibiotics after 48 hours if clinically improving, with total duration <7 days 1, 2

Special Populations

Critically Ill Patients

• Use meropenem 1g IV every 8 hours for healthcare-associated or high-severity infections 1
• Add vancomycin 25-30mg/kg loading dose if MRSA risk is present 1

Key Clinical Principles

• Extended-spectrum antibiotics offer no advantage over narrower-spectrum agents when adequate source control is achieved 2
• Timing is critical: preoperative antibiotics must be given 0-60 minutes before incision 2
• Source control is defined as complete appendectomy with no residual abscess or diffuse purulence 2